Exposure method and exposure device

ABSTRACT

An exposure method capable of performing accurate exposure without using a large photomask. The exposure method performs exposure while relatively moving a photomask above a substrate and includes a step of performing position correction of the photomask by performing, on a front side of the photomask relatively moved in a moving direction, image recognition of a pattern prearranged on the substrate such as a line and a black matrix and by correcting deviation of the photomask with respect to the pattern, and a step of checking the position correction of the photomask by performing image recognition of a reference mark arranged on the photomask and by determining whether or not the position correction of the photomask is accurately performed in the step of performing the position correction of the photomask.

This application is a continuation of U.S. patent application Ser. No.12/295,925 filed Oct. 3, 2008, which is the U.S. national phase ofInternational Application No. PCT/JP2006/324541, filed 8 Dec. 2006,which designated the U.S. and claims priority to Japan Application No.2006-104161, filed 5 Apr. 2006, the entire contents of each of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure method and an exposuredevice, and in particular relates to an exposure method and an exposuredevice which perform exposure while relatively moving a substrate and aphotomask.

2. Description of the Related Art

In a liquid crystal display panel, a pair of substrates are arrangedopposing to each other at a predetermined gap, and liquid crystals arefilled therebetween. On one of the substrates, constituents are stackedsuch as pixel electrodes which apply voltage to the liquid crystals,switching elements such as thin film transistors which drive the pixelelectrodes, various lines such as gate bus lines and source bus lines,and an alignment layer which provides a pretilt angle to the liquidcrystals. On the other substrate, constituents are stacked such as ablack matrix, color filter layers having predetermined colors, commonelectrodes, and an alignment layer.

An alignment process for aligning the liquid crystals toward apredetermined direction is applied to the alignment layers arranged onthe substrates. Conventionally, a rubbing process using a material suchas a textile material is used as the alignment process. However, aphotoalignment process has recently been used alternatively as thealignment process. The photoalignment process is a process that providespredetermined alignment characteristics on a surface of an alignmentlayer through a step to project light energy onto the surface of thealignment layer at a predetermined incident angle.

Constituents such as the switching element, the various lines, the blackmatrix, and the color filter layers are arranged using aphotolithographic process. For example, the color filter layer is formedthrough a step to coat the substrate surface with a photoresist materialhaving a predetermined color, a step to project light energy onto apredetermined pattern region on the photoresist material using aphotomask, and a step to remove an unnecessary portion of thephotoresist material (e.g. a portion onto which the light energy is notprojected).

As prior art literatures relating to the present invention, JapanesePatent Application Unexamined Publications Nos. 2005-024649 andHei11-133429 are cited.

An exposure step to project light energy onto a predetermined region ona surface of a substrate is indispensable in manufacturing of liquidcrystal display panels. If deviation in an exposure position and/or anexposure range occurs, conditions such as of alignment of liquidcrystals and of lines arranged on the substrate may become differentfrom the designed conditions, causing the substrate to fail to havedesigned alignment or characteristics. For example, if deviation in aposition and/or a range of light energy projection Occurs in theexposure step to provide the photoalignment process to the alignmentlayer, it becomes impossible to provide the designed pretilt angle tothe liquid crystals.

In addition, when projecting light energy onto the surface to beirradiated of the substrate using a photomask, the accuracy regardingthe position and/or the range of light energy projection issignificantly influenced by the dimensional accuracy of a pattern oflight shielding portions and light transmitting portions which arearranged on the photomask, thereby rendering the photomask to beexpensive. Moreover, the size of photomasks has been increased alongwith recent upsizing of substrates, resulting in even more expensivephotomasks.

Further, when a large photomask is used, problems tend to occur such aschange in the sizes of light shielding portions and light transmittingportions and deviation in alignment with the substrate, due to factorssuch as deformation and thermal expansion. Countermeasures against theproblems are performed for example by suppressing the change in thesizes by managing the temperatures of the substrate and the photomaskand by improving the accuracy of the mechanism for alignment and thecontrol thereof, but such countermeasures result in complicatedprocesses and increased running costs. Hence, the present invention aimsto provide an exposure method and an exposure device capable ofperforming accurate exposure without using a large photomask.

SUMMARY OF THE INVENTION

An object of the invention is to overcome the problems described aboveand to provide a method for performing exposure by projectingultraviolet light or other light onto some regions on a surface of asubstrate using a plurality of small photomasks having slit openingswhile moving the substrate. This method enables predetermined regions onthe substrate surface to be exposed in stripes (i.e. irradiated withultraviolet light or other light). In addition, while projectingultraviolet light or other light and moving the substrate, this methodsimultaneously photographs existing patterns prearranged on thesubstrate surface, for example, line patterns including gate bus lines,source bus lines, and a black matrix, and a reference mark arranged onthe photomask, in order to monitor the position onto which the light isactually projected, that is, the position of the photomask with respectto the existing patterns using a photographed image. By such exposuremethod, it is possible to perform exposure with high alignment accuracyregardless of the sizes of substrates.

Preferred embodiments of the present invention provides an exposuremethod which performs exposure while relatively moving a photomask abovea substrate and includes a step of performing position correction of aphotomask by performing, on a front side of the photomask relativelymoved in a moving direction, image recognition of a pattern prearrangedon the substrate and by correcting deviation of the photomask withrespect to the pattern, and a step of checking the position correctionof the photomask by performing image recognition of a reference markarranged on the photomask and by determining whether or not the positioncorrection of the photomask is accurately performed in the step ofperforming the position correction of the photomask.

It is preferable that a light transmitting window for performing theimage recognition of the pattern prearranged on the substrate isarranged on the photomask and the reference mark of the photomask isarranged on the light transmitting window.

In addition, it is also preferable that the image recognition of thepattern prearranged on the substrate and the image recognition of thereference mark of the photomask are performed using one camera, and itis further preferable if the camera is a bifocal camera.

Preferred embodiments of the present invention also provide an exposuredevice which performs exposure while relatively moving a photomask abovea substrate and includes a mechanism to perform position correction ofthe photomask by performing, on a front side of the photomask relativelymoved in a moving direction, image recognition of a pattern prearrangedon the substrate and by correcting deviation of the photomask withrespect to the pattern, and a mechanism to check the position correctionof the photomask by performing image recognition of a reference markarranged on the photomask and by determining whether or not the positioncorrection of the photomask is accurately performed by the mechanism toperform the position correction of the photomask.

It is preferable that a light transmitting window for performing theimage recognition of the pattern prearranged on the substrate isarranged on the photomask and the reference mark of the photomask isarranged on the light transmitting window.

In addition, it is also preferable that the image recognition of thepattern prearranged on the substrate and the image recognition of thereference mark of the photomask are performed using one camera, and itis further preferable if the camera is a bifocal camera.

The present invention allows to perform exposure with high alignmentaccuracy when the exposure is performed while the photomask isrelatively moved above the substrate, because the exposure method andthe exposure device according to the preferred embodiments of thepresent invention include the position correction of the photomask inwhich the image recognition of the pattern prearranged on the front sideof the photomask relatively moved in the moving direction and anydeviation of the photomask with respect to the pattern is corrected, andthe checking of the position correction of the photomask, in which theimage recognition of the reference mark arranged on the photomask isperformed and it is determined whether or not the position correction ofthe photomask is accurately performed by the above-described positioncorrection of the photomask.

If the photomask is configured such that the light transmitting windowfor performing the image recognition of the pattern prearranged on thesubstrate is arranged on the photomask and the reference mark of thephotomask is arranged on the light transmitting window, the lighttransmitting window and the reference mark can be provided in a normalmanufacturing process of the photomask. Accordingly, the cost tomanufacture the photomask does not increase.

In addition, if the image recognition of the pattern prearranged on thesubstrate and the image recognition of the reference mark of thephotomask are performed using one camera, it becomes possible tosimplify equipment for the image recognition, and the positioningaccuracy of the camera is improved as compared to the case of providingtwo cameras for both of the image recognitions.

Further, if the camera is a bifocal camera, it is possible tosimultaneously perform focus adjustment in the image recognition of thepattern prearranged on the substrate and focus adjustment im the imagerecognition of the reference mark of the photomask. Thus, recognizedimages are not blurred, thereby allowing easier image processing such asdetection of edges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic views illustrating a configuration ofmajor portions of an exposure device according to a preferred embodimentof the present invention, and FIG. 1A is an overhead view of theexposure device seen from above a surface to be irradiated of asubstrate, while FIG. 1B is a side view of the exposure device.

FIG. 2 is an external perspective view schematically illustrating aconfiguration of a photomask used in the exposure device illustrated inFIGS. 1A and 1B.

FIG. 3 is a view schematically illustrating the bifocal configuration ofa camera used in the exposure device illustrated in FIGS. 1A and 1B.

FIGS. 4A and 4B are schematic views illustrating a photoalignmentprocess of an exposure method or the exposure device according topreferred embodiments of the present invention. FIG. 4A illustrates aphotoalignment process on an array substrate, FIG. 4B illustrates aphotoalignment process on a color filter substrate, and FIG. 4Cillustrates alignment of liquid crystals in a pixel of a liquid crystaldisplay panel formed by bonding the above substrates together.

FIGS. 5A and 5B are views illustrating dimensional relation between aphotomask for an array substrate used in the photoalignment processillustrated in FIGS. 4A and 4B and a pattern prearranged on the arraysubstrate.

FIG. 6 is a view illustrating dimensional relation between a photomaskfor a color filter substrate used in the photoalignment processillustrated in FIGS. 4A and 4B and a pattern prearranged on the colorfilter substrate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A detailed description of preferred embodiments of the present inventionwill now be given with reference to the accompanying drawings. FIGS. 1Aand 1B are schematic views illustrating a configuration of majorportions of an exposure device according to a preferred embodiment ofthe present invention, and FIG. 1A is an overhead view of the exposuredevice seen from above a surface to be irradiated of a substrate, whileFIG. 1B is a side view of the exposure device.

An exposure device 1 includes a plurality of exposure units 11 whichproject light energy onto a surface to be irradiated of a substrate 3,and a table 12 which supports and moves the substrate 3. Arrows a inFIGS. 1A and 1B indicate the moving direction of the substrate 3 on thetable 12.

Each of the exposure units 11 has an exposure head 111, a light source112, a photomask 2, a camera 113, a photomask movement mechanism 114, astorage mechanism 115, and a comparison mechanism 116. By arranging aplurality of the exposure units 11 in a zigzag configuration in adirection perpendicular to the moving direction a of the substrate 3 asillustrated in FIG. 1A, the whole surface to be irradiated of thesubstrate 3 can be exposed.

As the light source 112 of the exposure unit 11, various known lightsources may be used which can emit light energy in a predeterminedwavelength band, and a suitable light source is selected according tocircumstances such as a purpose of irradiation and the type of an objectto be irradiated. For example, an ultraviolet light source is used whenprojecting ultraviolet light onto the surface to be irradiated of thesubstrate 3.

The photomask 2 which is used for exposure is arranged such that thesurface thereof is substantially parallel to the surface to beirradiated of the substrate 3 as an ordinary state. In addition, thephotomask 2 is hold such that it is located below the exposure head 111and movable on a plane, which is parallel to the surface to beirradiated of the substrate 3, to a direction b which is perpendicularto the moving direction a of the substrate 3.

The photomask 2 is a transparent substrate made of silica glass or othermaterial on which light transmitting portions and light shieldingportions are arranged in a predetermined pattern. FIG. 2 is an externalperspective view schematically illustrating a configuration example ofthe photomask 2. An arrow a in FIG. 2 indicates the moving direction ofthe substrate 3. On the photomask 2, vertically long slits defining thelight transmitting members 22 are arranged side by side with apredetermined pitch along a direction perpendicular to the movingdirection a of the substrate 3. In FIG. 2, a region on which hatching isapplied is the light shielding portions 21 while regions on whichhatching is not applied are the light transmitting portions 22.

A horizontally long slit defining a light transmitting window 23 isarranged on the photomask 2 on a front side of the photomask 2 movedrelative to the substrate 3 in a moving direction, and a reference mark24 defining an alignment mark of the photomask 2 is arranged on thelight transmitting window 23.

The camera 113 is capable of photographing the surface to be irradiatedof the substrate 3 which is placed on the table 12. A knownphotographing device such as a CCD camera may be used as the camera 113.As illustrated in FIG. 1B, the camera 113 is arranged on the exposurehead 111 on a front side of the exposure head 111 moved relative to thesubstrate 3 in a moving direction.

The camera 113 photographs an existing pattern 4 including a gate busline, a source bus line, and a black matrix, which is prearranged on thesubstrate 3. Here, the camera 113 photographs the existing pattern 4 inorder to perform image recognition of a line from the starting edge tothe ending edge of the existing pattern 4 which is arranged in parallelto the moving direction a of the substrate 3 (which is illustrated as avertical line in FIG. 1A). Accordingly, the image recognition of theexisting pattern 4 moving under the light transmitting window 23 isperformed by photographing the existing pattern 4 using the camera 113.

In case the existing pattern 4 moving under the light transmittingwindow 23 deviates toward a direction perpendicular to the movingdirection a of the substrate 3 while the camera 113 photographs theexisting pattern 4, an amount of the deviation is calculated and thephotomask 2 is moved for alignment adjustment according the deviationamount. The alignment adjustment is performed by the above movementcontrol of the photomask 2 following the existing pattern 4, therebyallowing accurate exposure of a position along the existing pattern 4.

In addition to photographing the existing pattern 4 moving under thelight transmitting window 23, the camera 113 simultaneously photographsthe reference mark 24 arranged on the light transmitting window 23. Whenthe photomask 2 is moved to correct the deviation while the camera 113photographs the existing pattern 4 as described above, the referencemark 24 being photographed also moves. At this time, an amount of themovement of the reference mark 24 is calculated, and it is determinedwhether or not the movement of the photomask 2 for alignment adjustmenthas been accurately performed. If the determination result indicatesthat the photomask has not moved, or the movement amount is considerablygreater than the calculated deviation amount, an action such as stoppingof the exposure process is performed.

Each of the photomasks 2 is provided with the camera 113. Additionally,each of the cameras 113 is made independently movable by a movementmechanism (not shown) which differs from the movement mechanism used tomove the photomask 2. The movement mechanism for the camera 113 is usedfor purposes such as alignment with the photomask 2 performed beforestarting exposure.

The camera 113 is a bifocal camera having two focal points asillustrated in FIG. 3 which is capable of focusing on each of theexisting pattern 4 on the substrate 3 and the reference mark 24 andclearly photographing both of them. As illustrated in FIG. 3, a lightadjustment plate 113 a is interposed between a half of the view field ofthe camera 113 and the photomask 2 so as to simultaneously focus on theexisting pattern 4 on the substrate 3 and the reference mark 24 of thephotomask 2 which have different focal depths.

The storage mechanism 115 stores a reference image used to align thephotomask 2 and is capable of further storing an image of the existingpattern 4 and an image of the reference mark 24 of the photomask 2 whichare photographed by the camera 113.

The comparison mechanism 116 compares the image of the existing pattern4 on the substrate 3 which is photographed by the camera 113 and thereference image stored in the storage mechanism 115 and determinespositional relation between a region of the surface to be irradiated ofthe substrate 3 onto which the light energy is actually projected and aregion onto which the light energy is designed to be projected, in otherwords, determines an amount of positional deviation of the photomask 2with respect to the existing pattern 4.

The photomask movement mechanism 114 corrects the deviation by movingthe position of the photomask 2 based on the deviation amount determinedby the comparison mechanism 116 so that the light energy is actuallyprojected onto the region of the surface to be irradiated of thesubstrate 3 onto which the light energy is designed to be projected.

In addition, the comparison mechanism 116 compares an image of thereference mark 24 of the photomask 2 photographed by the camera 113before the position of the photomask 2 is corrected by the mask movementmechanism 114 and an image of the reference mark 24 of the photomask 2photographed by the camera 113 after the position of the photomask 2 iscorrected, determines an amount of the movement of the photomask 2 whichhas been performed to correct the position, and determines whether ornot the correction of the position of the photomask 2 is accuratelyperformed. If the determination result indicates that the photomask hasnot moved, or the movement amount is considerably greater than thecalculated deviation amount, an action such as stopping of the exposureprocess is performed. If the movement amount of the photomask 2 is equalto the determined deviation amount, the exposure process continues.

The light energy is projected onto the substrate 3 while moving thesubstrate 3, and the alignment adjustment of the photomask 2 isperformed following the existing pattern 4 as described above. Then, theexposure process terminates when the existing pattern 4 moves under thephotomask 2 from the starting edge to the ending edge.

By using the image of the existing pattern and the image of thereference mark 24 of the photomask 2 photographed by the camera 113,positional relation between the existing pattern 4 and the photomask 2is monitored during exposure. Accordingly, it is possible tosignificantly improve the accuracy of the alignment of the photomask 2with respect to the existing pattern 4.

Next, an implementation example according to the preferred embodiment ofthe present invention is described. The implementation example describedherein is a photoalignment process which is applied to an alignmentlayer to form a plurality of regions having different alignments ofliquid crystals (hereinafter referred to as domain regions) in eachpixel of a liquid crystal display panel. In this implementation example,ultraviolet light is used as light energy to be projected.

FIGS. 4A and 4B are schematic views illustrating projection forms oflight energy projected onto pixels which are arranged on each of a pairof substrates that form a liquid crystal display panel, namely, an arraysubstrate and a color filter substrate. FIG. 4A illustrates a pixelarranged on the array substrate, while FIG. 4B illustrates a pixelarranged on the color filter substrate. FIG. 4C is a schematic planeview illustrating alignments of liquid crystals in a pixel of the liquidcrystal display panel formed by bonding the above substrates together.

As illustrated in FIG. 4A, a pixel electrode 313 is arranged in a regionsurrounded by source bus lines 312 and gate bus lines 311, and a thinfilm transistor 313 which drives the pixel electrode 313 is arranged inthe vicinity of an intersection of the source bus line 312 and the gatebus line 311 on the array substrate. In addition, on a surface of apixel 31, an alignment layer made of polyamide or other material isarranged (not shown).

On the color filter substrate, as illustrated in FIG. 4B, a pixel 32 isdefined by the black matrix 321, and a color filter layer 322 isarranged inside the pixel 32. In addition, a common electrode and analignment layer are arranged on a surface of the pixel 32 (not shown).

As configurations and manufacturing methods of the array substrate andthe color filter substrates, conventional configurations andmanufacturing methods are applicable, and thus descriptions thereof areomitted herein.

As illustrated in FIG. 4A, a photoalignment process of the arraysubstrate involves two regions in the pixel 31 formed by dividing thepixel 31 in two at its substantial center line between the source buslines 312 arranged on the sides. Alternate long and short dashed lines Ain FIG. 4A indicate the boundary of the regions. Ultraviolet light isprojected from a direction inclined at a predetermined angle θ to thenormal to the surface of the pixel 31 onto each of the regions of thealignment layer. The directions of the ultraviolet lights projected ontothe regions are such that, given that the optical axes of theultraviolet lights are projected onto the surface of the pixel 31, theprojected axes are substantially parallel to the source bus line 312,and the directions of the projected axes are 180 degrees opposite toeach other.

A photoalignment process of the color filter substrate involves tworegions formed by dividing the pixel 32 in two at its substantial centerline between the two sides of the black matrix which are parallel to thegate bus lines 311 of the array substrate when the color filtersubstrate is bonded together with the array substrate. Alternate longand short dashed lines B in FIG. 4B indicate the boundary of theregions. Ultraviolet light is projected from a direction inclined at apredetermined angle θ to the normal to the surface of the pixel 32 ontoeach of the regions of the alignment layer. The directions of theultraviolet lights projected onto the regions are such that, given thatthe optical axes of the ultraviolet lights are projected onto thesurface of the pixel 32, the projected axes are substantially parallelto the gate bus lines 311, and the directions of the projected axes are180 degrees opposite to each other.

When the array substrate and the color filter substrate to which thephotoalignment processes are applied are bonded together, the liquidcrystals filled between the substrates are aligned according to thedirections of the photoalignment processes applied to the regions of thesubstrates, that is, the directions of the projections of theultraviolet lights. Arrows in FIG. 4C schematically illustratealignments of the liquid crystals. In each pixel, four domain regionsare formed which are different to each other in alignment directions ofthe liquid crystals.

FIG. 5A is a view illustrating a configuration of a photomask used toapply the photoalignment process to the alignment layer of the arraysubstrate in the implementation example (hereinafter referred to as anarray substrate photomask). FIG. 5B is a schematic plane viewillustrating relations in terms of dimensions and positions between thearray substrate photomask and a pattern of pixels arranged on the arraysubstrate.

Similar to the photomask 2 shown in FIG. 2, an array substrate photomask2 x is a plate member which has a substantially rectangle shape and ismade of silica glass or other material. As illustrated in FIG. 5A, aplurality of light transmitting portions 22 x capable of transmittingultraviolet light are arranged substantially parallel to each other witha predetermined pitch. A pitch P_(x) of the light transmitting portions22 is set to be equal to a pitch of the source bus lines 312 arranged onthe array substrate as illustrated in FIG. 5B. The width of the lighttransmitting portion 22 x is set to be equal to about the half length ofthe pitch P_(x). In addition, a light transmitting window 23 x isarranged on the array substrate photomask 2 x, and a reference mark 24 xis arranged on the light transmitting window 23 x. An arrow a in FIG. 5Bindicates the moving direction of the array substrate with respect tothe array substrate photomask 2 x.

Using the array substrate photomask 2 x, ultraviolet light is projectedat a predetermined incident angle onto one of the two regions formed bydividing the pixel at its substantial centerline between the source buslines 312. Then, ultraviolet light is projected onto the other region ata predetermined incident angle. The relation between the incident anglesof the ultraviolet lights projected onto the regions are as describedabove. It is possible to project ultraviolet light onto each of the tworegions using the single array substrate photomask 2 x by shifting theposition of the array substrate photomask 2 x with respect to the arraysubstrate by the half length of the pitch P_(x) of the lighttransmitting portions in a direction perpendicular to the movingdirection a of the array substrate.

FIG. 6 is a schematic plane view illustrating relations in terms ofdimensions and positions between a photomask used to apply aphotoalignment process to the alignment layer arranged on the surface ofthe color filter substrate in the implementation example (hereinafterreferred to as a color filter substrate photomask) and the pixelsarranged on the color filter substrate.

The configuration of a color filter substrate photomask 2 y is basicallythe same as that of the array substrate photomask 2 x except for thedimensions of light transmitting portions 22 y. As illustrated in FIG.6, a pitch P_(y) of the light transmitting portions 22 y is set to beequal to the pitch of the sides of the black matrix 321 which areparallel to the gate bus lines of the array substrate. The width of thelight transmitting portions 22 y is set to be equal to about the halflength of the pitch P_(y). In addition, a light transmitting window (notshown) which is similar to the light transmitting window 23 x of thearray substrate photomask 2 x is arranged on the color filter substratephotomask 2 y, and a reference mark is arranged on the lighttransmitting window. An arrow a in FIG. 6 indicates the moving directionof the color filter substrate with respect to the color filter substratephotomask 2 y.

Using the color filter substrate photomask 2 y, ultraviolet light isprojected at a predetermined incident angle onto one of the two regionsformed by dividing the pixel at its substantial center line between thesides which are parallel to the gate bus lines of the array substrate.Then, ultraviolet light is projected onto the other region at apredetermined incident angle. The relation between the incident anglesof the ultraviolet lights projected onto the regions is as describedabove. It is possible to project ultraviolet light onto each of the tworegions using the single color filter substrate photomask 2 y byshifting the position of the color filter substrate photomask 2 y withrespect to the color filter substrate by the half length of the pitchP_(y) of the light transmitting portions 22 y in a directionperpendicular to the moving direction a of the color filter substrate.

As described above, the present invention provides a method to performexposure by projecting ultraviolet light or other light onto someregions on a surface of a substrate using a plurality of smallphotomasks having slit openings, while moving the substrate. By thismethod, it is possible to perform exposure with high alignment accuracyregardless of sizes of substrates.

In addition, while projecting ultraviolet light or other light andmoving the substrate, the method simultaneously photographs an existingpattern prearranged on the substrate surface, such as a line patternincluding a gate bus line, a source bus line, and a black matrix, and areference mark of the photomask to monitor using a photographed imagethe position onto which the light is actually projected, in other words,monitor the position of the photomask with respect to the existingpattern on the substrate. The above procedures enable the exposuremethod according to the present invention to be performed with highaccuracy.

The foregoing description of the preferred embodiments and theimplementation example of the present invention has been presented forpurposes of illustration and description with reference to the drawings.However, it is not intended to limit the present invention to thepreferred embodiments, and modifications and variations are possible aslong as they do not deviate from the principles of the presentinvention.

For example, the present invention is applied to a photoalignmentprocess of an alignment layer of a liquid crystal display panel in thedescriptions above; however, it is not limited thereto. The presentinvention is applicable to exposure performed using photolithographictechnique to provide color filter layers, a black matrix, and othercertain constituents.

1. An exposure method to project ultraviolet light or other light ontoan alignment layer on a substrate to form a plurality of regions havingdifferent alignment directions in each pixel of the substrate, whereinthe light energy is projected onto the alignment layer through aphotomask while moving the substrate, and alignment adjustment of thephotomask is performed following an existing pattern which isprearranged on the substrate, by comparing the image of the existingpattern and the image of a reference mark arranged on the photomask. 2.The exposure method according to claim 1, wherein the reference mark isarranged on a front side of the photomask in a moving direction.
 3. Theexposure method according to claim 2, wherein the reference mark isarranged on a horizontally long slit defining a light transmittingwindow.
 4. The exposure method according to claim 1, wherein theexisting pattern is one selected from the group of a gate bus line, asource bus ling, and a black matrix.
 5. The exposure method according toclaim 1, wherein the ultraviolet light is projected from a directioninclined at a predetermined angle to the normal to the surface onto eachof the regions of the alignment layer of the pixel.
 6. The exposuredevice according to claim 5, wherein the directions of the projectedaxes onto each of the regions of the alignment layer of the pixel are180 degrees opposite each other.
 7. The exposure method according toclaim 1, wherein the image recognition of the existing patternprearranged on the substrate and the image recognition of the referencemark of the photomask are performed using one camera.
 8. The exposuremethod according to claim 1, wherein the camera is a bifocal camera. 9.The exposure method according to claim 1, wherein on the photomask,vertically long slits defining the light transmitting members arearranged side by side with a predetermined pitch along a directionperpendicular to the moving direction of the substrate.
 10. The exposuremethod according to claim 9, wherein a pitch of the light transmittingmembers is set to be equal to a pitch of the source bus lines arrangedon the array substrate.
 11. The exposure method according to claim 9,wherein a pitch of the light transmitting members is set to be equal toa pitch of the black matrix.
 12. The exposure method according to claim1, wherein the exposure process terminates when the existing patternmoves under the photomask from the starting edge to the ending edge.